This PR adds a new modal component and its styles. It will be used in the next PR to solve #30
It also creates a new set pre-defined styles for buttons: 'primary' | 'secondary' | 'tertiary' | 'white' | 'primary2' | 'primary-red' | 'secondary-red'here
'primary' | 'secondary' | 'tertiary' | 'white' | 'primary2' | 'primary-red' | 'secondary-red'here<img width="200" src="https://github.com/gnolang/gnomobile/assets/689440/75453b28-c395-47c9-ae9f-96adca1be5e9" />